Aeration method for establishing gas lift in oil wells



Dec. 17, 1929. 4F. w. LAKE 1,740,104

AERATION METHOD FOR ESTABLISHING GAS LIFT IN OIL WELLS Filed July 3.8,1927 sansman@@www .wfiw

ATTORNEY Patented Dee.y 1 7, 1929 f UNITED ISTATES PATENT OFFICE FRANCISW. LAKE, OF WHITTIER, CALIFORNIA, ASSIGNOR TO UNION OIL COMPANY OFCALIFORNIA, OF LOS ANGELES, CALIFORNIA, A CORPORATION OF CALIFORNIA iAERATION METHOD FOR ESTABLISHING GAS LIFT IN OIL WELLS Application filedJuly 18, 1927. Serial No. 206,680.

This invention relates to the so-called gas lift method of flowing deepwells, particularly oil wells,

itiation methods, is disclosed and claimed in my companionapplications,A Serial Numbers 206,677 and 206,681.

Gas lift, as now commonly practiced, consists in passing gas underpressure into a well containing a flow tube, so that the gas passesaround the lower end of the flow tube in a stream and in its passageatomizes theoil as fast as it is forced up to said tube end by thenatural rock pressure in the well, the atomized oil being carried to thesurface in the gas stream.` The gas may be introduced either through theflow tube or through the casing, the atomized oil being discharged fromthe other of the two; however, it is preferred usually to introduce thegas into the casing and discharge the oil from the flow tube.

In attempting to establish normal gas lift in some wells where the gasis to be introduced into the casing, it is frequently found that thereis great loss in pressure between the point of introduction of the gasand the point of contact of said gas with the body of the oil in thelower end of the casing. This loss in pressure may be due to any one ormore of several causes. For example, said pressure loss may be due tothe presenceof a barren or low pressure sand open to the well, or to acasing which is so leaky as to allow the escape of gas in suicientamounts to prevent the building up of a pressure suiicient to force outthe head of oil. Again, the pressure drop may be duefto friction,especially in the deeper wells where the casing weaves from side toside, thereby causing the flow tube 4to contact the casing or toapproach the same so closely as to materially reduce the space betweenthe tube and the casing at many points;

and has been designed to overl come the excess hydrostatic head of oilwhich p this is particularly true where the tube is large relative tothe casing.

In vmany of such cases, the available gas ressurevwould be suflicient toestablish gas lift upon application of pressure to the casing, if itwere not for the conditions which induce the pressure drop and if themaximum pressure could be maintained. Under able gas pressure isinsufcient to start gas lift through the flow tube by the application ofpressure in the casing merely because of said pressure loss.

The object of the invention is to present a method for applying the gaspressure which will prevent losses of high p ressure gas and will enablethe discharge of the hydrostatic head standing in the flow tube and theinitiation of gas lift regardless of whatever losses result from saidcauses.

To accomplish this result, it has been found possible to reverse thenormal direction of gas flow into the well, that is, to flow the gasthrough the tube into the casing. Since the tube usually is intact andthereby prevents pressure loss by leakage, the gas pressure then issufficient (due to absence ofsuch leakage or other loss) to overcome thehydrostatic head standing in the lower end of the tube so as to expelthe accumulated column of oil therefrom and cause a flow of. gas underthe lower end of the tube into the oil body within the casing insuiicient quantities to thoroughly aerate the oil and to atomize atleast a portion thereof and carry the same upward and out through thecasing vent. This operation may be, and usually is, continued until asufficient quantity of the oil body has been discharged to eliminate thestatic head and to bring the oil level down to a point approximating thelower end of the tube so that upon directing the gas flowinto thecasing, normal gas lift up through the tube will commence. In clearingthe well with the y'casing vented, since the pressure in the casing isactually much lower than that in the tube, leaks from the casing underthis low pressure are'insignificant as are those from the casing afterthe head has been eliminated/and ygas lift instituted,

vsuch conditions, however, the highest avail- Thus, the invention,generically stated comprises initiating gas lift in an oil well having acasing containing a body of accumulated oil into which a flow tubedepends and wherein .material pressure losses from the casing areencountered due to casing leaks, open sands or the like, by applying gasto the flow tube under a pressure at least suflicient to force the oilout of the iiow tube and to force said gas up through the oil in thecasing to acrate, atomize and discharge the'oil from the casing, thedirection of flow according to a preferred form being then reversed tomaintain gaslift.

In the 'accompanying drawing wherein various steps in the operation ofthe method are diagrammatically represented:

Fig. 1 indicates the introduction of the gas through the fl'ow tubeto'reduce the hydrostatic head in a leakycasing;

Fig. 2 represents the final establishment of gas lift up through the Howtube of Fig. 1, gas being introduced through the leaky casing afterelimination of the oil head;

Fig. 3 indicates the introduction of gas through the flow tube to reducethe hydrostatic head in a well wherein the tube depends below the casingso that gas, if applied, to the casing, will be-lost to the sands whenthe oil level is depressed to the lower end of the casing; and

Fig. 4 indicates the establishment of normal gas lift up through theflow tube upon elimination of the hydrostatic head of Fig. 3.

In Fig. 1 there is represented a well having a leaky casing 10, theholes or perforated portions which account for the leaks being indicatedat 11. Into this casing, the usual flow tube 12 depends and enters theoil body which has accumulated therein and risen to the level 14. Valvedconnections 15 and 16 leading from a gas compressor C are re'-spectively connected with the casing and the ow tube, so that gas underpressure may be appliedV to either. A valve controlled oil and gasoutlet 18 is also provided on the casing. In this instance, when gas isapplied through the connection 15 to the casing for the purpose ofdepressing the oil level, the outlet 18 beino closed, so much pressureis lost through the leaky portions 11 that the resultant pressure isinsuilicient to force over the oil head and cause gas lift to beestablished through the flow tube. However, by opening the outlet 18 andintroducing the gas under pressure through the flow tube, the fullpressure of the gas is made available and succeeds in overcoming thehead in the tube so as to expel the oil therefrom and cause the gas toflow upward through the oil body. The introductionof gas is thencontinued in suicient quantities to atomize the oil and carry the sameupward and outward through outlet 18, and ordinarily this is continueduntil the oil level has been lowered to the bottom of the flow tube asindicated at 2() in Fig. 2.' Inasmuch as the casing is vented under thiscondition, the loss of gas through the leaky portion 11 under thereduced pressure in the casing is not appreciable. If desired, they flowof the well in this direction'may be continued. However, ordinarily theflow of gas is reversed upon proper depression of the level byintroducing the gas through connection 15 and expelling the oil from thetop of the tube 12 as indicated in Fig. 2. Since tn; gas pressure nowrequired to flow the well (that is by atomizing the oil,) is much lessthan that required to expel the head, the loss of gas through the leakyportions becomes relatively insignificant.

Sometimes the condition represented in Fig. 3 exists wherein the flowtube depends to a point opposite the sands. In this instance, ifpressure is applied in the casing, part of the same is lost into thesands as soon as theV oil level has been depressed to the upper limit ofthe oil bearing stratum. However, the gas may be introduced through thetube l2 and allowed to flow around the lower end thereof and up throughthe oil body thereby atomizing the latter and discharging the same fromthe casing in the same manner as described above, and the direction ofthe introduction of gas reversed, if desired, when the oil level hasbeen reduced to the lower end of said tube, as indicated in Fig. 4.

During the aeration step, the body of oil is so thoroughly charged withgas, both by absorption and by mechanical entrainment, that uponrestoration of the normal direction of flow such entrained gas will, byexpansion, materially assist the establishment of the gas liftoperation.4 In fact, this advantage is so evident that it is not alwaysnecessary to lower the oil body to the end of the flow tube'by theatomizirrg-e'ect. It is to be understood that this method ofestablishing reverse flowand then establishing normal How, mayconstitute the entire method of initiating gas lift, or it mayconstitute only the final steps thereof. For example, it is possible'toemploy as an initial ste other methods for charging the oil body wlthgas,

and after such preliminar steps have been taken, reverse-flow can e morequickly established by reason of the lightened ycondition attained inthe oil body by the absorption and entrainment of gas.

n It is to be understood, of course, that after reverse flow is onceestablished, that is, by passing gas through the tubing into the casingand flowing out through the caslng, gas

lift may be continued in such reverse direction,.if desired, since it isnot always necessary to return to the normal flow upward through thetubing. In any event the major purpose of the invention isthe'introduction of'` gas into the oil body in suiclent quantities andfor a sufficient length of time to thoroughly liven up and remove anappreclable part of the heavy head of dead oil which stands in the welland which requires to be removed before normal gas lift can beestablished. The method may be considered obtained, the control of suchintroduction being managed in the same fashion as above described. A

As an example of one method of practicing the invention, in an instancewhere loss from the casing was so great that pressure therein could notbe built up above 300 it, a pressure-ot1 500 if: was applied to thetube. This was sufficient to -force the oil out of the tube andestablish gas lift up through the casing until the oil head was removed,whereupon the gas was reversed to flow up through the tube and thepressure was dropped to17 5 :li to continue gas lift. 4

The above disclosures are to be considered not as limiting but as merelyillustrative, and many variations ofl the invention may be made withinthe scope of the following claims.

I claim:

l. A method for gas lift in an oil well having a casing and tubedepending thereinto, comprising introducing gas under pressure to one ofsaid members for atomizing and discharging oil from the other, and thenreversing the gas flow to establish normal gas lift` operation in theopposite direction.

2. A method for' gas lift in an oil well containing a well casing and aflow tube depending tiereinto, wherein it is desired to establish gaslift for discharging oil from the top of the flow tube, comprisingintroducing gas under pressure into the flow tube and causing it to passbeneath the lower end of the' fiow tube into the oil body within thecasing and to atomize a portion of said oil body and discharge the samefrom the casing. continuing such operation until the oil leve has droped to a point to insure normal gas lift, an reversing the gas flow byintroduction of gas into the casing and under the lower end of the flowtube whereby the oil is atomized inthe How tube and discharged therefrom,thus establishing normal operation.

3. A method for gas lift inan oilwell containing a casing and adepending vflow tube,

flow tube under pressure comprising in a direction opposite to that inwhich it is desired to establish normal iiow, causing said gas to passbeneath the lower end of the iow tube and upward through Athe oil bodyto charge the same with gas and atomize a portion thereof, continuingthe How to discharge a portion of said oil body, and then reversing thegas flow to cause it to pass in the opposite direction under the lowerend of said iow tube and establish normal gas lift operation. i

4. Ina method for initiating gas lift in anv oil well containing acasing in which a body of oil has accumulated and within which a flowtube depends into the oil, and where there is a material pressure lossfrom the casing, the steps of passing gas into the which is sufficientnormally to overcome the hydrostatic head of oil in the tube, butinsufficient to overcome said head and said pressure loss combined, andflowing said gas from the lower end of the tube into the oil'body in thecasingto charge the same with gas.

5. A method according to claim 4 wherein gas flow is continued to anextent to atomize a portion of the oil body and' discharge it from thecasing-to lower the oil level therein.

6. A method for initiating gas lift in an oil well having a casing fromwhichl material pressure losses are encountered and wherein a flow tubedepends into a body of oil accumulated in the well, comprising applffinggas a pressure su clent to therein out of the iow tube-and forcing saidgas up through the oil in the casing to atomize and discharge the samefrom the casing to lower the oil level to a point approximating thelower end of the low tube, and then reversing the direction of gas ilow.

7. In a method according to claim 4 the additional steps of continuinggas ilow to an extent to atomize a portion of the oil body anddischargeit from the casing to cause the oil level therein to drop,andthen reversing the gas iow to cause it to pass in the ofppositedirection and establish normal gas li Signed at Los Angeles, in thecounty of Los Angeles and State of California, this 12th day of July, A.D. 1927.y v

FRANCIS W. LAKE.

to the low tube under force the oil standing Iintroducing gas underpressure

